From patchwork Fri Mar 23 18:49:58 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Peter Maydell X-Patchwork-Id: 890147 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=linaro.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 407CTl5Rx5z9s0b for ; Sat, 24 Mar 2018 05:57:47 +1100 (AEDT) Received: from localhost ([::1]:39401 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ezRsn-0006xP-Ar for incoming@patchwork.ozlabs.org; Fri, 23 Mar 2018 14:57:45 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49188) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ezRlR-00019P-C5 for qemu-devel@nongnu.org; Fri, 23 Mar 2018 14:50:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ezRlP-0004Hi-TD for qemu-devel@nongnu.org; Fri, 23 Mar 2018 14:50:09 -0400 Received: from orth.archaic.org.uk ([2001:8b0:1d0::2]:40514) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ezRlP-0004GT-M7 for qemu-devel@nongnu.org; Fri, 23 Mar 2018 14:50:07 -0400 Received: from pm215 by orth.archaic.org.uk with local (Exim 4.89) (envelope-from ) id 1ezRlO-0007ho-DG for qemu-devel@nongnu.org; Fri, 23 Mar 2018 18:50:06 +0000 From: Peter Maydell To: qemu-devel@nongnu.org Date: Fri, 23 Mar 2018 18:49:58 +0000 Message-Id: <20180323184958.14252-11-peter.maydell@linaro.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180323184958.14252-1-peter.maydell@linaro.org> References: <20180323184958.14252-1-peter.maydell@linaro.org> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2001:8b0:1d0::2 Subject: [Qemu-devel] [PULL 10/10] target/arm: Always set FAR to a known unknown value for debug exceptions X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" For debug exceptions due to breakpoints or the BKPT instruction which are taken to AArch32, the Fault Address Register is architecturally UNKNOWN. We were using that as license to simply not set env->exception.vaddress, but this isn't correct, because it will expose to the guest whatever old value was in that field when arm_cpu_do_interrupt_aarch32() writes it to the guest IFSR. That old value might be a FAR for a previous guest EL2 or secure exception, in which case we shouldn't show it to an EL1 or non-secure exception handler. It might also be a non-deterministic value, which is bad for record-and-replay. Clear env->exception.vaddress before taking breakpoint debug exceptions, to avoid this minor information leak. Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé Message-id: 20180320134114.30418-5-peter.maydell@linaro.org --- target/arm/op_helper.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c index 8e1e521193..a266cc0116 100644 --- a/target/arm/op_helper.c +++ b/target/arm/op_helper.c @@ -490,6 +490,11 @@ void HELPER(exception_bkpt_insn)(CPUARMState *env, uint32_t syndrome) { /* FSR will only be used if the debug target EL is AArch32. */ env->exception.fsr = arm_debug_exception_fsr(env); + /* FAR is UNKNOWN: clear vaddress to avoid potentially exposing + * values to the guest that it shouldn't be able to see at its + * exception/security level. + */ + env->exception.vaddress = 0; raise_exception(env, EXCP_BKPT, syndrome, arm_debug_target_el(env)); } @@ -1353,7 +1358,11 @@ void arm_debug_excp_handler(CPUState *cs) } env->exception.fsr = arm_debug_exception_fsr(env); - /* FAR is UNKNOWN, so doesn't need setting */ + /* FAR is UNKNOWN: clear vaddress to avoid potentially exposing + * values to the guest that it shouldn't be able to see at its + * exception/security level. + */ + env->exception.vaddress = 0; raise_exception(env, EXCP_PREFETCH_ABORT, syn_breakpoint(same_el), arm_debug_target_el(env));